1. The Field of the Invention
The invention generally relates to driving optical components. More specifically, the invention relates to compensating driving signals of optical components to compensate for environmental or devices differences.
2. Description of the Related Art
Modern day computer networks allow for transmissions of large amounts of data between computer terminals. Data may be transmitted on a network across a number of different mediums. For example, data may be transmitted across traditional copper wire based cables. However, copper wire based cables are subject to limitations that are making them less attractive as a solution for many modern networks. Specifically, the copper wire based cables are limited in the amount of data they can carry in a given time period and the length that the data can travel. As computer technology continues to increase in the amount of data that can be produced in a given time period, other types of cable with higher capacities and longer transmission distances may be desirable.
One type of cable that is capable of higher data transmission rates over longer distances is fiber-optic cable. Fiber-optic cables are plastic or stretched glass cables that carry data signals in the form of light. Light signals can propagate on fiber-optic cables at higher speeds and for longer distances than electronic signals on copper wire based cables. Further, fiber-optic cables are potentially lighter weight and less expensive than their copper based counterparts. Thus, fiber-optic cables are steadily becoming a more popular choice for communication networks.
While fiber-optic data signal are optical or light signals, data signals at computer terminals generally continue to be electronic data signals. The electronic data signals being sent by a computer terminal are therefore converted using an electro-optical transducer, such as a laser diode or light emitting diode (LED) that converts the electronic data signals to corresponding optical data signals. To receive a signal from a fiber-optic network, a computer terminal converts the optical data signal to a corresponding electronic signal using an opto-electronic transducer, such as a photodiode and post-amplifier.
A laser diode emits laser light at varying power levels when a varying power level electronic signal is applied to anode and cathode terminals of the laser diode. Thus a modulated optical signal can be produced directly from a corresponding modulated electronic data signal using a laser diode. In one exemplary configuration, a laser may be modulated by digital data to produce an optical signal, including periods of light and dark output that represents a binary data stream. In actual practice, the lasers output a high optical output representing binary highs and a lower power optical output representing binary lows. To obtain quick reaction time, the laser is constantly on by being biased by a DC bias current, but varies from a high optical output to a lower optical output by being modulated by an AC modulation current.
There is often a need to control or monitor the actual power being output by a laser diode or LED. Digital optical signals are often required to be within a certain optical power level. The optical output of laser diodes for a given current through the laser diode is dependant on factors such as temperature. As the ambient temperature in which a laser diode operates increases, without intervention, bias and modulation currents will also increase. This will affect the optical power output. To maintain appropriate power levels, there is a need to compensate for temperature fluctuations.